Thursday, August 9, 2007 - 11:10 AMCOS 112-10: Marine aerosols alter soil processes in coastal forests
Jana E. Compton1, M. Robbins Church1, and Yuko Asano2. (1) US EPA, NHEERL, Western Ecology Division, (2) The University of Tokyo
Most models of watershed biogeochemistry include the movement of materials from land to rivers and eventually the ocean. Few conceptual views, however, acknowledge the influence of materials derived from the ocean on terrestrial ecosystem processes. Based on spatial patterns of stream chemistry in the Oregon Coast Range, we hypothesize that deposition of marine aerosols stimulates nitrate leaching from coastal forest soils. Salt deposition may influence nitrate dynamics through a number of mechanisms. We were able to induce nitrate leaching by adding salt solutions in lab experiments using root-free soils. Direct exchange of chloride for nitrate did not occur, but strong salt solutions did displace ammonium from the exchanger, which was nitrified over time. Lab salt additions also decreased the leaching of dissolved organic carbon, which has implications for the cycling of nitrogen and net nitrate production. In field experiments, addition of dilute sodium chloride solutions depressed soil respiration, indicating a biotic response at salt concentrations comparable to coastal deposition values. Our field experiment also showed a lag time between addition of salt and when it appeared in high concentrations in lysimeters. We used stable isotopes of water to assist in understanding the influence of soil flowpaths on biogeochemistry. Our findings of an interaction between marine aerosol inputs and soil processes represent a new perspective on nutrient dynamics in near coastal ecosystems.